1. Field of the Invention
Generally, the invention relates to machines to install a series of depressions in the surface of a road. More specifically, the invention relates to such machines which utilize a plurality of camming groups, which move in an endless loop, to regulate an elevational movement of a rotary cutting tool.
2. Description of the Prior Art
It has been known for some time that the installation of a series of depressions into a surface of a road adjacent a normal driving lane significantly reduces accidents along the road. This is the result of an operator of a motor vehicle being informed, by the vibration and/or noise created by contact of the tires of the motor vehicle with the depressions, that the motor vehicle has left the normal driving lane.
Generally, the series of depressions, sometimes referred to as ‘SNAP’ or ‘sonic noise alert pattern’, will be installed along a defining boundary of the road. These boundaries are along the road adjacent an edge of the normal driving area. For divided highways, where the driving area is designed for unidirectional travel, these boundaries exist on both sides of the road and may have multiple driving lanes therebetween. For bidirectional highways these boundaries exist on the left hand side and optionally, may exist at a center line separating the traffic moving in opposing directions. Similarly, the driving area for each direction of travel may have multiple driving lanes thereon.
The series of depressions may be continuous or may have a skip pattern incorporated therein. Specifications may vary from state to state and even within a particular state. These specifications define overall size and depth of each depression as well as relative placement within the overall series, all within predefined ranges of accuracy.
One example of a set of specifications for a series of depressions, used herein only for illustration, has each depression having a rectangular shape at the surface of the road with a measurement of about sixteen inches across and about seven inches in length aligned with the driving lane. The series will be outside of the normal driving area, but in close proximity thereto. Due to the milling procedure employed, each depression will have an arced base from rearward trailing edge to forward leading edge with a depth of about one half (½) of an inch at the center portion. Numerous specifications require one (1) depression installed for each linear foot of surface. This results in an uncut section of surface between each adjacent pair of depressions of about five inches. Therefore, the continuous series would result in the installation of fifty-two hundred and eighty (5280) depressions per mile. One common configuration for skip pattern installation eliminates four (4) sequential installations within each grouping of twelve (12) continuous series installation. This results in an elimination of one-third (⅓) of the depressions present in the continuous series. Therefore, this skip pattern series would result in the installation of thirty-five hundred and twenty (3520) depressions per mile.
Without regard for the type of installation employed, continuous or skip, certain areas of the road will typically be excluded from the installation procedure. Examples of such areas include along bridges, along intersections, along entrance and exit ramps and sometimes adjacent motorist aid call boxes.
Numerous methods exist to install the series of depressions into the surface of the road. While it is possible to install the depressions using other methods, as exampled by stamping for asphalt, the following examples are specific to rotary cutting tools, as applicable to the present invention.
It has long been known to install the series using a repetitive series of advance, pause, plunge cut cycles utilizing a single cutting tool. This is an extremely inefficient method of installing the series and may result in a series having variation in spacing between each adjacent pair of depressions. For these reasons this type of installation is rarely used today in the industry.
It is known to install the series using a similar pause while utilizing multiple cutting tools. Due to the dimensioning of the individual depressions it is not possible to position adjacent cutting tools in a position to install two (2) adjacent depressions which have the proper spacing therebetween. Therefore, when utilizing such machines having three (3) or more cutting tools it is common to have two (2) separate and distinct advancement cycles. One of the advancement cycles will be equal to the spacing of adjacent depressions within the resultant series. The second will be of a measurement to clear those depressions formed by the prior two (2) installation cycles. This method also is extremely inefficient and may result in a series having variation in spacing between each adjacent pair of depressions. For these reasons this type of installation is rarely used today in the industry.
An innovation over the pause and plunge cut method described above has been to continuously advance the installation machine and the rotary cutting tool while regulating the elevation of the rotary cutting tool to move the rotary cutting tool downward into contact with the surface of the roadway and upward out of contact with the surface of the roadway. Examples of such methods are disclosed in several of applicants seven prior U.S. Patents and the references listed thereunder. The conventional continuous advance method allow for continuous advance of the installation machine with the milling procedure mechanically regulated. It is conventionally known to regulate a lowering action and a raising action of the cutting tool during the advance to provide for the desired spacing between installations as well as the proper dimensioning of the depressions.
Examples of elevational regulation of rotary cutting tools to install a series of depressions include regulatory devices rolling along the surface of the road, such as cam wheels, regulatory devices which are positioned above the surface of the road but rotationally controlled by the speed of the machine, and electronic control devices which measures the advance speed of the machine and control the down and up movement of the rotary cutting tool accordingly. Typically the mechanical regulation machines are less expensive to manufacture and typically provide more precise installations than those machines which rely upon electronic control over the cutting cycles. A deficiency which exist with the mechanical regulation machines involve wear to the regulation surfaces, either those in contact with the surface of the roadway or those which regulate the lowerings and raisings of the rotary cutting tool. Currently when worn beyond acceptable limits replacement of the entire regulatory unit must be made.
Referring now to installation of skip pattern series of depressions, conventional continuous advance installation machines often will utilize a simple mechanical counting method with elimination of the lowering action during the desired gap in the series. An example of the conventional methods of eliminating the lowering action involves either raising the cutting assembly so that the conventional elevation regulation does not reach the surface during the lowering or by otherwise mechanically blocking the cutting assembly in a raised position. A deficiency with some of the known methods of implementing elimination of installations for skip pattern installations with machines capable of continuous installation involve the relatively high speed of installation currently known and the weight of the rotary cutting tool assembly. When a mechanical raising of the rotary cutting tool assembly, such as by hydraulic drive, is implemented often the rotary cutting tool will make at least slight contact with the surface of the roadway at the location of the first skipped cut. While less of a problem, due to the weight of the rotary cutting tool assembly, the first cut after the skipped group may not be fully formed to match the subsequent cuts.
Various deficiencies exist with the conventionally known methods of installing series of depressions. Various attempts have been made to provide for an installation machine capable of installing depressions in a series where precise control over the installation occurs to precisely match the specifications of the particular installation. These attempts have been less efficient than desired. As such, it may be appreciated that there continues to be a need for an installation machine which is versatile and dependable and which may be easily and reliable adjusted to provide for consistent installation of either continuous series of depressions or skip pattern series of depressions. The present invention substantially fulfills these needs.